Connecting FrightProps Sensor Beam to Prop 2

[Spooky Dad]

EFX Forum - I am using three 4-wire sensor beams (details on them below) with a prop-2 for initiating a wall of skeletons to start rocking back and forth via wiper motors.  While I have the program working with a PIR, I can not get it to work yet with the sensor beam.  I was trying to use the PNP-NO configuration (page C6-17) of the sensor beam to trip input (P12, P11 and P10).  The question is, when I trip the sensor beam (not yet hooked up to Prop-2) in the NPN-NO configuration (Brown to V+ that is 12V, Blue and White to Ground, Black will be connected to White on wiring harness as input) the voltage jumps from 2.3 volts to 12 volts.  Will that hurt the prop-2?  Should I clip Pins 2 through 4 on the upper ULN2803 chip to protect from voltage overload?  Just looking for a bit of sanity before hooking up power.  Thanks!


Details on the sensor beam can be found on page C6-06 at the following URLS - http://www.progreen.co.in/files/documents/FP50-RECT-PHOTOELECTRIC-SENSORS.pdf

[JonnyMac]

For the Prop-1/Prop-2 you should only use NPN N.O.  In this mode, the output is just like the ULN: when not active, it's like a disconnected wire; when active, it connects to ground (please verify that your sensor is doing that).

To use an NPN device you must clip the associated ULN pin and move the SETUP jumper to the UP position. You must also set the trigger state in your programs: 1 = no trigger, 0 = active trigger.

[Spooky Dad]

Thanks JonnyMac.  That is the guidance I needed.  I see now that I was not consistent with the wiring schema (PNP versus NPN) below.  Sorry.  I will take it one at a time (clipping the pin on the ULN2803) and report back. 

[Spooky Dad]

JonnyMac - Just wanted a confirmation that in order to protect the ULN from the sensor beam input, that I will remove pins 4, 5 and 6 on the top ULN, which is equivalent to P12, P11, and P10, respectively.  Going off of the information in this post.

http://www.efx-tek.com/php/smf/index.php?topic=130.0

[JonnyMac]

If you're going to use an "open" sensor, you must have a pull-up (preferred) or pull-down on the line. This means you should be using P15..P12 for these type sensors. If you've got a simple PIR or other active-high sensor, you can use other pins with the ULN input circuitry intact, as this will act as a pull-down.

[Spooky Dad]

Got it.  Duh?  So now that I will use P15, P14 and P13, I need to cut off the legs (pins) 1,2 and 3 on the upper ULN on the prop-2, correct?

[JonnyMac]

Yes.

I know that your sensor offers a PNP mode, but we can't take a chance on it outputting 12v and damaging the board. Using NPN (outputting ground) on a pin with a pull-up is always safest.

An 5v sensor can be used on another pin that has the ULN circuitry intact. Even a N.O. button or switch between Px.R and Px.W will work.

[Spooky Dad]

Thanks JonnyMac and sorry I was not clear.  The "duh" was a comment towards me about specifying the wrong pins that did not provide the ability to pull-up.  I definitely plan on using the NPN configuration of the sensor beam.  The reason we are going for the sensor beam is that we need the ability to precisely detect a victim before triggering a haunted portrait.

So, with that said, now that it is confirmed I am using the NPN configuration of the sensor beam and using P15, P14 and P13 for the input triggers, I would cut the legs (pins) 1,2 and 3 of the upper ULN on the prop-2, right?

[JonnyMac]

Again, yes.

And any of those inputs that are NPN N.O. need to have the SETUP jumper set to the UP position.

[Spooky Dad]

Thank you.  I will post completed prop program and design.